Which font is used in Blender's logo?
It is a special version of Helvetica. You can check the below links:

https://blenderartists.org/forum/showthread.php?67062-Official-Blender-font

https://blenderartists.org/forum/showthread.php?114438-Blender-s-Font

https://blenderartists.org/forum/showthread.php?90755-Blender-Font